A polonium nucleus, while at rest, decays into a lead nucleus of rest mass 342.1
ID: 2112550 • Letter: A
Question
A polonium nucleus, while at rest, decays into a lead nucleus of rest mass 342.1126 x 10^-27 kg, and emits a helium nucleus of rest mass 6.6483 x 10^-27 kg. In this reaction momentum and total energy are conserved. After the decay, the helium nucleus moves with a speed of 1.6 x 10^7 m/s.
Kinetic energy of helium nucleus = 8.51 x 10^-13 J
Speed of lead nucleus = -310929.21 m/s
KE of lead nucleus = 1.6537 x 10^-14 J
Mass that is transformed into KE = 9.6393 x 10^-30 kg
Determine the rest mass of the Polonium nucleus?
Explanation / Answer
Sums of masses of daughters: (342.1126*10^-27 + 6.6483*10^-27) = 3.49*10^-25 kg
Mass Defect of KE of Alpha: (1/2) (6.6483*10^-27) (1.6*10^7)^2/(3*10^8)^2 = 9.46*10^-30 kg
Total = polonium rest mass = 3.4877035536*10^25 kg